Block copolymers are known to be useful in a variety of contexts. For example, U.S. Pat. No. 3,766,300, issued to De La Mare Oct. 16, 1973 discloses the rapid hydrogenation of copolymers prepared from conjugated dienes and polar monomers such as vinylpyridines, which are said to be useful as compatibilizers or polydispersants.
U.S. Pat. No. 3,891,721 issued to Prudence Jun. 24, 1975 discloses block polymers having the architecture C-B-A where C is styrene, B is butadiene and A is 2-vinylpyridine. There is no mention of polyisoprene midblocks. These polymers are said to have high tensile strength.
U.S. Pat. No. 3,567,798 issued to Haefele et al. Mar. 2, 1971 relates to block copolymers with a configuration C-B-C-A where C is a relatively low molecular weight vinyl arene block (4,000-20,000 mw), B is a conjugated diene in which the molecular weight is not critical (5,000-200,000 mw) and A is 1-100 units of a monomer which can be a monovinylpyridine, (meth)acrylic acid ester, (meth)acrylonitrile, monovinylquinoline or acrylamide. Again, tensile strength is said to be improved.
U.S. Pat. No. 3,639,523 issued to Hayter et al. Feb. 1, 1972 relates to adhesives having improved green strength, building tack, solvent resistance and high temperature stability. The architecture of the disclosed polymer is A-C-B-C-A where A is vinylpyridine, B is a conjugated diene, and C is a monovinyl arene. None of the above references disclose or suggest the use of these polymers as radiation curable materials.
Triblock copolymers having poly(4-vinylpyridine) end blocks and a polybutadiene center block can be prepared by sequential anionic polymerization of butadiene and of 4-vinylpyridine using an organolithium initiator; see M. S. Jacovic, "Ionomer-like materials based on 4-vinylpyridine copolymers," Maromol. Chem., Rapid Commun, Vol. 10, 217-225 (1989).
Quaternization of triblock polymers of polystyrene-polybutadiene-polyvinylpyridine is disclosed by Ohnuma et al. in Chemical Abstracts, 111(16):134883 (1989).
Quaternization of poly(4-vinylpyridine) is known: Boucher et al., "Kinetics and Mechanism of the Quaternization of Poly(4-vinylpyridine) with Ethyl, n-Propyl, n-Butyl, n-Hexyl and Benzyl Bromide in Sulfolane", J. Chem. Soc. Faraday Trans. I, 73, pp. 629-1635 (1977).
Diblock and triblock copolymers of butadiene and 2-isopropenylpyridine have been synthesized by anionic polymerization, using a difunctional lithium initiator: Soum et al., "Synthesis and Characterization of New Block Copolymers of Butadiene and 2-isopropenylpyridine," Polymer, vol. 29, pp. 1528-1534 (August, 1988).
Triblock copolymers of polystyrene-polybutadiene (or polyisoprene)-polystyrene have been used in the preparation of photosensitive printing plates: U.S. Pat. No. 4,323,637, Chen et al., "Use of Cover Sheet and Interposed Flexible Film with Block Copolymer Compositions" (1982). The copolymers were not quaternized, nor were the resulting formulations water-developable.
U.S. Pat. No. 4,162,919, Richter et al. (1979), discloses a 2-block copolymer of styrene-isoprene (or butadiene) for use in flexographic printing plates.
U.S. Pat. No. 4,245,027, Takeda et al. (1981), discloses a photosensitive composition comprising copolymers of vinylpyridine and a polyvinylidene halide, optionally with an olefin, e.g., butadiene or isoprene, plus a light sensitizing element, e.g., iodoform, quinones, or diazonium salts, capable of forming a quaternary salt with the polyvinylpyridine on heating or on exposure to actinic light. The instant invention differs, inter alia, in that the triblock copolymer has no polyvinylidene halide component, and further in that it is quaternized prior to formulation and exposure.
U.S. Pat. Nos. 4,271,259 and 4,272,610, both to Breslow et al. (1981), disclose a copolymer of butadiene or isoprene with vinyl pyridine as a component in a photosensitive composition. The copolymer is not specified as ABA, and it is not quaternized. The composition requires an oxidizable component containing allylic hydrogen and a photooxygenation sensitizer.
U.S. Pat. No. 4,430,417, Heinz et al. (1984), discloses ABA triblock copolymers in making flexographic printing plates. A is styrene-butadiene, B is isoprene
U.S. Pat. No. 4,179,531, Heinz (1979), discloses ABA triblock copolymers ("Kraton".RTM.--Shell Chemical Co.) in making printing plates where A is a styrene and B is a diene such as isoprene or butadiene. A polythiol is required in the formulation.
U.S. Pat. No. 4,045,231, Toda et al. (1977), discloses a styrene-butadiene-styrene triblock copolymer in a printing plate formulation.
Chem. Abstracts 111(6):39978k, Moeller et al., discloses iodine doped AB diblock copolymers of poly(2-vinylpyridine) and either polybutadiene or polystyrene.
Chem. Abstracts 109(10):74182b, Shimazaki et al., discloses triblock copolymer, polystyrene-polyisoprene-poly(vinylpyridine) quaternized with chloromethylstyrene. Use in photosensitive compositions is not disclosed.
Chem. Abstracts 104(20):169705k, Y. Mihaki, discloses isoprene-styrene-4-vinylbenzyldimethylamine block copolymers treated with di-iodopropane to prepare an amphoteric ion exchanger.
Chem. Abstracts 103(20):166031f, Lelah et al., discloses quaternization of triblock poly(styrenebutadiene-4-vinylpyridine), with crosslinking of the butadiene segment and sulfonation of the styrene block.
Chem. Abstracts 101(6):39114u, Kudose et al., discloses quaternizing triblock butadiene-styrene-4-vinylpyridine copolymer with methyl bromide.
Chem. Abstracts 88(2):75242, Fielding-Russell et al., discloses HCl quaternization of butadiene-styrene-2-vinylpyridine block copolymer.
Copending U.S. Ser. No. 729,976, filed Jul. 15, 1991, describes the use of ABA triblock copolymers of vinylpyridine-isoprene-vinylpyridine and their corresponding quaternized block copolymers as flexographic printing plates developable in aqueous surfactant systems. It was seen that the quaternized block copolymers were hazy. It was later found that neutralization of the vinylpyridine blocks with a strong acid such as trifluoroacetic acid led to clear, non-hazy thick plates. Copending U.S. Ser. No. 868,062, filed Jul. 15, 1991, is a continuation-in-part of U.S. Ser. No. 729,976 which discloses the manufacture and use of those acid neutralized triblock copolymers. Both applications are incorporated herein by reference as if set forth in full.